Patent Literature 1 discloses, as a device that detects the values on capacitors distributed in a matrix manner, a capacitance detecting circuit that detects a distribution of the electrostatic capacitances of capacitors arranged in rows and columns demarcated by M drive lines and L sense lines. The capacitance detecting circuit, which capitalizes on a decrease in capacitance of a capacitor at an area touched with a finger or a pen, detects a contact area corresponding to a touch of a finger or a pen on the touch panel by detecting a change in capacitance.
FIG. 15 is a schematic view showing a configuration of a conventional touch panel device 900. Further, FIG. 16 is a diagram for explaining a method for driving the touch panel device 900. The touch panel device 900 includes a touch panel 902 and a touch panel controller 903. The touch panel 902 has drive lines DL1 to DL4, sense lines SL1 to SL4, and capacitors C11 to C44 disposed in locations at intersections between the drive lines DL1 to DL4 and the sense lines SL1 to SL4. Further, the touch panel controller 903 has a drive portion 904 and amplifiers 908.
The following will describe how the touch panel device 900 converts the electrostatic capacitances into measurement values (detection values).
The drive portion 904 drives the drive lines DL1 to DL4 on the basis of a 4×4 code sequence shown in (Exp. 3) of FIG. 16. The drive portion 904 applies a voltage VDD when an element of the code sequence is “1”, and applies a zero voltage in the case of an element “0”.
The touch panel device 900 has four amplifiers 908 disposed so as to correspond to the sense lines SL1 to SL4, respectively. The four amplifiers 908 receive and amplify linear sums Y1 to Y4 of electric charges on capacitors along with the sense lines SL1 to SL4 driven by the drive portion 904, respectively.
Specifically, in the first round of driving of the four rounds of driving based on the 4×4 code sequence, the drive portion 904 applies the voltage VDD to the drive line DL1 and applies a zero voltage to the remaining drive lines DL2 to DL4. Then, for example, through the sense line SL3, an output corresponding to an electric charge of the capacitor C31 as indicated by (Exp. 1) of FIG. 16 is fed as a measurement value Y1 to the amplifier 908.
Then, in the second round of driving, the drive portion 904 applies the power supply voltage VDD to the drive line DL2 and applies a zero voltage to the remaining drive lines DL1, DL3, and DL4. Then, through the sense line SL3, an output corresponding to the capacitor C32 as indicated by (Exp. 2) of FIG. 16 is fed as a measurement value Y2 to the amplifier 908.
Similarly, in the third round of driving, the drive portion 904 applies the power supply voltage VDD to the drive line DL3 and applies a zero voltage to the remaining drive lines. After that, in the fourth round of driving, the drive portion 904 applies the power supply voltage VDD to the drive line DL4 and applies a zero voltage to the remaining drive lines. Through the third round of driving and the fourth round of driving, the measurement values Y3 and Y4 are obtained corresponding to the electrostatic capacitances C33 and C34, respectively.
In this manner, as indicated by (Exp. 3) and (Exp. 4) of FIG. 16, the measurement values Y1, Y2, Y3, and Y4 are associated with the electrostatic capacitances C31, C32, C33, and C34, respectively.